The College of William & Mary has landed its biggest private gift ever — $50 million — as it begins a school-record $1 billion fund-raising campaign, a landmark development for the venerable public school founded in colonial Virginia.

The eye-catching numbers, announced Thursday night in Williamsburg, are the latest sign of public higher education’s growing reliance on private philanthropy in an era of dwindling state support for colleges and universities.

Several big-name public schools have ongoing campaigns for $1 billion or more. The University of California at Los Angeles is shooting for $4.2 billion, and the University of Michigan seeks $4 billion. The University of Virginia wrapped up a successful $3 billion effort in 2013.

Among private universities, Harvard has the largest fund-raising target with a goal of $6.5 billion, according to the Council for Advancement and Support of Education. The University of Southern California is seeking $6 billion.

Drumming up donations is difficult and costly, requiring sophisticated “advancement” teams and deep engagement with alumni. For private colleges, this is routine. But until recently that has not necessarily been the case for public colleges because they have counted more on annual appropriations from state legislatures.

Now, in an era of tight state funding and rising costs, prominent public institutions have few options if they want to stay competitive and continue to offer major discounts on tuition for in-state students.

“Philanthropy is the absolute life’s blood of the schools that are going to succeed in this century, public and private,” said William & Mary President Taylor Reveley. “We’re after it tooth and claw.”

Taylor Reveley (courtesy William & Mary)

William & Mary, with about 8,400 students, said it is the smallest public university in the nation to embark on a $1 billion fund drive. The campaign is an ambitious undertaking for a university without a medical or engineering school. Doctors and engineers are often crucial sources of higher education philanthropy.

Founded in 1693, William & Mary was the second college in the English colonies. (The first was Harvard, in 1636.) It did not become a state-supported institution until 1906, a shift Reveley said was meant to remedy financial troubles dating to the Civil War. As recently as 1980, Virginia supplied 43 percent of its operating revenue. Now, Reveley said, the state contribution is down to 12 percent.

“Which means we’ve got to find 88 cents of every dollar we spend from somewhere else,” he said in a telephone interview with The Washington Post.

William & Mary’s first private funding drive, in the 1970s, raised more than $20 million. Its second, from 1986 to 1993, collected $153 million. Its third, from 2000 to 2007, netted $517 million.

The latest drive, Reveley’s first since he became president in 2008, got under way in what is known as a “quiet phase” in July 2011 and ramped up two years later. The original target in that phase was $600 million, but as donations mounted the school set its sights higher.

“Six hundred million doesn’t get the blood flowing,” Reveley said. “A billion, on the other hand, is a round number with some body and flavor.”

As they made the announcement, William & Mary officials said they are more than halfway toward meeting the target, with commitments for donations totaling more than $532 million. That includes what is now the school’s biggest gift. A married couple, both alumni who wished to remain anonymous, pledged $50 million for scholarships to attract top law and business students and for other purposes.

The school’s previous record for an announced gift was $23.9 million in 2013 from the Walter J. Zable estate for athletic scholarships, stadium renovations and other purposes.

William & Mary, known as a mid-sized research university with the feel of an intimate liberal arts college, is perennially among the nation’s top-ranked schools. U.S. News and World Report ranks it 34th this year among national universities, and sixth among those that are public.

Tuition and fees at William & Mary total $19,372 for freshmen from Virginia (with the tuition portion, $13,978, fixed for four years). For those from out of state, tuition and fees are $41,072. Those prices don’t include a $10,978 charge for room and board, or other expenses for books and travel. Virginia law requires the school to preserve at least 65 percent of its undergraduate slots for state residents.

William & Mary’s endowment stands at about $800 million.

In previous years, the school would boost its fundraising staff at the outset of a campaign and then draw down at the conclusion. This time officials plan to keep the machinery going indefinitely, much as private universities do.

“We intend to be in perpetual campaign mode now,” said Matthew T. Lambert, vice president for university advancement.